Study of Electroactive Polymers as Corrosion Inhibitors of Aluminum 2024-T3 and Cold Rolled Steel. Conducting Polymers of Corrosion Control of Coated Aircraft

摘要

Chromate surface treatments and chromate-containing epoxy primers are often used for corrosion control of aluminum alloys. However, due to environmental concerns and adverse health effects surrounding such use of chromates, there is an intensive effort to find suitable replacements for chromate-based coatings. Electroactive conducting polymers (ECPs) continue to be of considerable interest as components of corrosion-resistant coating systems. ECPs, in addition to being conductive, are redox active materials, with potentials that are positive of iron and aluminum. Thus, as with chromate, interesting and potentially beneficial interactions of ECPs with active metal alloys are anticipated. Our group has been investigating several ECPs for their corrosion protective properties, with emphasis on solution processable polymers. In this final report, the results of long-term immersion, preliminary results of Prohesion(registered) exposure studies, and scanning vibrating electrode technique (SVET), also known as the current density probe (CDP), are described. The coating systems studied incorporated either poly (3-octyl pyrrole) (POP) or poly (3-octadecyl pyrrole) (PODP) as a primer coating of 2 to 3 micrometers thickness. Samples were also studied that utilized a polyurethane topcoat of ca. 20 micrometers thickness in conjunction with the ECP coating. In control experiments, a chromated-epoxy primer of 20 micrometers thickness replaced the ECP coating. The immersion solution for the aluminum 2024-T3 samples was dilute Harrison solution, consisting of 0.35% (NH4)2SO4 and 0.05% NaCl. For the cold rolled steel samples a 3% NaCl electrolyte was used for this study.